1. Field of the Invention
This invention relates to optical scanners and microscopes.
2. Discussion of the Related Art
Several imaging techniques perform an optical scan of a sample and form a two-dimensional (2D) image of the sample from measured intensities of light emitted by the scanned spots of the sample. Herein, spots of the sample refer to portions of the sample that a focused beam of light is able to illuminate. One imaging technique is two-photon microscopy. In two-photon microscopy, a sample spot emits light as a result of a two-photon absorption event.
Two-photon microscopy often produces higher image resolutions than standard scattering-based microscopy. One reason for the higher resolution is that a two-photon microscope eliminates background light associated with scattering of scan light in the sample. This background light is eliminated by filtering light to remove the scan wavelength prior to measuring the intensities of light emitted by scanned spots. The filtering does not attenuate two-photon induced light, because the two-photon induced light has a different wavelength than the scan light. Another reason for the higher resolution is that a two-photon microscope has an inherently smaller scanned spot than a scattering-based microscope. The smaller spot results, because two-photon events are limited to a high-intensity portion of a spot that is smaller than the portion in which one-photon scattering occurs.